Raising the Mexican Tetra <em>Astyanax mexicanus</em> for Analysis of Post-larval Phenotypes and Whole-mount Immunohistochemistry

Abstract

River and cave-adapted populations of Astyanax mexicanus show differences in morphology, physiology, and behavior. Research focused on comparing adult forms has revealed the genetic basis of some of these differences. Less is known about how the populations differ at post-larval stages (at the onset of feeding). Such studies may provide insight into how cavefish survive through adulthood in their natural environment. Methods for comparing post-larval development in the laboratory require standardized aquaculture and feeding regimes. Here we describe how to raise fish on a diet of nutrient-rich rotifers in non-recirculating water for up to two-weeks post fertilization. We demonstrate how to collect post-larval fish from this nursery system and perform whole-mount immunostaining. Immunostaining is an attractive alternative to transgene expression analysis for investigating development and gene function in A. mexicanus. The nursery method can also be used as a standard protocol for establishing density-matched populations for growth into adults.

Host evolution shapes gut microbiome composition in Astyanax mexicanus

“…In most other species it is not possible to compare divergent populations and a representative ancestor in a controlled laboratory setting. A. mexicanus is easy to grow and manipulate in the lab, standardized husbandry protocols are published (Riddle, Martineau, et al., 2018 ), the genome is sequenced and annotated (Warren et al., 2021 ), and there are a growing number of resources available to examine and manipulate gene function (Stahl, Jaggard, et al., 2019 ). Furthermore, methods for deriving germ‐free zebrafish, and inoculating them with specific microbes could be applied to A. mexicanus (Melancon et al., 2017 ).…”

“…In addition, we found stable differences in the abundance of Fusobacteriota between laboratory‐raised populations suggesting that taxa abundance could be used as a quantitative trait for genetic mapping in A. mexicanus as has been done in mice (Kemis et al., 2019 ; Zhang et al., 2023 ). Our study defines the variables that shape the microbiome in a model system that will continue to impact our understanding of ecology and evolution due to its unique phylogeny (Herman et al., 2018 ; Ornelas‐García & Pedraza‐Lara, 2015 ), amenability to laboratory manipulation (Peuß et al., 2019 ; Riddle, Martineau, et al., 2018 ), and genetic accessibility (Klaassen et al., 2018 ; Stahl, Peuß, et al., 2019 ).…”

Little Fish, Big Questions: A Collection of Modern Techniques for Mexican Tetra Research

“…They simplify this multi-day procedure using a checklist (provided as a supplementary file) and share guidelines for troubleshooting. Complementary to this method, Riddle et al 34 show how to examine gene expression and protein localization in hatched fish using wholemount immunohistochemistry.…”

Genetic mapping of metabolic traits in the blind Mexican cavefish reveals sex-dependent quantitative trait loci associated with cave adaptation

“…Gonad development in A. mexicanus has not been explored, but it is conceivable that the cave environment may have selected for altered reproductive strategies. Cavefish eggs are larger than surface fish eggs and cavefish tend to have smaller clutch sizes [19,20]. The markers with the highest LOD scores for gonad weight appear on linkage group 1 (41.8 cM), 19 (75.4 cM), and 22 (143.9 cM) and account for 14%, 13%, and 12% of phenotype variance respectively (Table 6).…”